The present invention is generally directed to polythiophenes and uses thereof. More specifically, the present invention in embodiments is directed to electronic devices, such as thin film transistors (TFT), containing a novel class of polythiophenes, especially poly(perfluoroalkylthiophenes) wherein certain repeating thienylene units possess perfluoroalkyl and alkyl side chains, which are arranged in a regioregular manner on the polythiophene backbone, and which polythiophenes are, for example, useful as active semiconductor materials in thin film transistors. In embodiments the polythiophenes, which can be comprised of, for example, two monomers such as 3-alkylthiophene and 3-perfluoroalkylthiophene in various effective proportions, possess the ability to self-organize when coated from their solutions into molecularly ordered thin films. The self-organization is a result, it is believed, of the intermolecular interaction between the side chains.
The polythiophenes of the present invention are, for example, derived from perfluoroalkylthiophene and alkylthiophene or alkoxythiophenes, and more specifically, by copolymerization of two monomers, an alkylthiophene or alkoxythiophene, and a perfluoroalkylthiophene by a metal halide-mediated coupling reaction, or from an alkyl or alkoxy-2,5-dihalothiophene and a perfluoroalkyl-2,5-dihalothiophene by regioregular copolymerization. These poly(perfluoroalkylthiophene)s generally possess excellent solution stability, and are suitable for solution fabrication processes.
Semiconductor polymers, such as certain polythiophenes, which are useful as active semiconductor materials in thin film transistors (TFTs), have been reported. A number of these polymers have some solubility in organic solvents and thus can be fabricated as semiconductor channel layers in TFTs by solution processes, such as spin coating, solution casting, dip coating, screen printing, stamp printing, jet printing and the like. Fabrication by common solution processes could render the manufacturing of TFTs by a noncomplex cost effective manner in comparison to the costly conventional photolithographic processes typical of silicon-based devices such as hydrogenated amorphous silicon. TFTs fabricated with polymer materials on flexible substrates, such as plastic films, provide structural flexibility and generally better mechanical properties, and which TFTs are useful for large area devices, such as large area image sensors, electronic paper and other display media where structural flexibility and mechanical robustness are of value. Also, the selection of polymer TFTs for integrated circuit logic elements for low-end microelectronics, such as smart cards, radio frequency identification (RFID) tags, and memory/storage devices, may also greatly enhance their mechanical durability, and thus their useful life span. Nonetheless, a number of the semiconductor polythiophenes may not be suitable for fabrication in ambient environments since they tend to be oxidatively doped by atmospheric oxygen, resulting in increased conductivity, thus in larger off-current and lower current on/off ratio for the devices fabricated from these materials. Accordingly, with many of these materials, rigorous precautions have to be undertaken during materials processing and device fabrication to exclude environmental oxygen to avoid or minimize oxidative doping. These precautionary measures add to the cost of manufacturing, therefore offsetting the appeal of certain polymer TFTs as an economical alternative to amorphous silicon technology, particularly for large area devices. These and other disadvantages are avoided or minimized in embodiments of the present invention.